The invention relates to a reclining chair frame of the type, in particular, used in dentistry.
Conventional chair frames with adjustable seat and back-rest, especially those installed in dentists' surgeries, consist fundamentally of a base, seat, and back-rest; the seat is carried by the base, and the back-rest hinged to the seat. Such chairs provide three basic adjustments, namely, raising and lowering of the seat (height), back-rest angle (rake), and simultaneous rotation or tilt of seat and back-rest (posture). Separate controls are provided for the three types of movement.
A chair of this kind is singularly useful for the purposes of dental treatment, since it enables the dentist to maneuver the patient from a sitting to a reclining position as and when may be necessary, according to the type of treatment being carried out.
Nonetheless, the conventional design of chair frame presents the drawback that increased rake causes the patient's head to move away through, in effect, a circular arc, thus becoming distanced from the point occupied by the dentist. This problem is heightened by the fact that the modern surgery contains numerous items of equipment, generally laid out in a circumferential array having its center at the spot normally occupied by the dentist, in the interests of ergonomic efficiency. It follows therefore, that if the position of the patient's head is altered, the dentist must necessarily stray from his/her preferred station, i.e. the point from which all of the various items of equipment can be reached without difficulty.
In practice, certain operations are carried out with the patient in a sitting position, whereas others require a reclining position; it becomes impossible, therefore, to establish an exact station for the dentist to adopt with the end in view of laying out equipment to best advantage.
Another requirement that may be encountered during a session of treatment is that of having to arrange the patient in haste with his/her head positioned on a level below that of the legs. This posture, known in medical circles as the Trendelenburg, is provided for in certain conventional types of chair, but obtainable only by way of additional movements and controls that complicate the chair's construction of the chair, and in addition to the disadvantage of a complicated structure, one has the drawback that a dentist will in practice use such a facility but rarely, and thus not always achieve its operation with the requisite speed.
The object of the invention disclosed is that of embodying a reclining chair frame with an adjustable seat and back-rest, in particular for use in dentistry, that is free from the drawbacks thus described.